This is a twelve week, double-blind, placebo-controlled, multicenter, randomized efficacy and safety study of budesonide nebulizing suspension involving approximately 450 patients throughout approximately 30 clinical centers. Patients will be evaluated during a 2 week baseline phase, after which they will be randomized to one of five double-blind nebulized treatments for 12 weeks. During the 12 week double-blind treatment phase, randomized patients will be scheduled to report to the clinic five times to be evaluated for efficacy and safety.